This invention relates to a connection structure for conductively connecting covered wires (conductor) with each other or connecting a covered wire to another member.
As a conventional connection structure of this kind of covered wire, an art proposed by this applicant (see Japanese Unexamined Published Patent Application No.Hei7-320842) will be described.
When connecting two covered wires an outer periphery of which is coated with a cover portion made of resin, at their intermediate connection portions, a pair of resin chips which are of resin material, a horn for producing ultrasonic vibration, and an anvil for supporting the covered wires and the resin chips at the time of connection are utilized.
The anvil comprises a base stand and a support portion projecting from the base stand. The support portion is formed in a substantially cylindrical shape. The support portion has a bore portion which is open to a counter-side of the base stand. Two pairs of grooves are formed in the peripheral wall of the support portion so as to confront each other of the respective pairs across substantially a center of the bore portion. The four grooves are formed so as to open to the same side as the bore portion, extending along the projection direction of the support portion and intercommunicate with the confronting ones through the bore portion.
A pair of resin chips are formed in a disc shape having a slightly smaller outer diameter than the diameter of the bore portion of the anvil. Furthermore, an end portion of a head portion of the horn is formed in a disc shape having an outer diameter which is slightly smaller than that of the resin chips.
In order to connect the two covered wires to each other, both of the covered wires are overlapped with each other at connection portions thereof and the overlapped portions are pinched by a pair of resin chips from up and down. Specifically, one of the resin chips (the resin chip at the lower side) is inserted into the bore portion of the anvil such that the melting surface thereof is directed upward. Then, one covered wire is inserted into one pair of the confronting grooves from the upper side of the inserted resin chip. Then, the other covered wire is inserted into the other pair of the confronting grooves. Finally, the other (upper side) resin chip is inserted such that the melting surface is directed downward. The covered wires are arranged in the bore portion such that the respective connection portions thereof cross each other at the center of the bore portion. Through this arrangement, the connection portions of the covered wires are pinched substantially at the center of the melting surfaces of the upper and lower resin chips in the overlapping direction.
Subsequently, the cover portions at the connection portions of the covered wires are melted so as to be dispersed by ultrasonic vibration. Furthermore, the conductive wire portions (core) of the covered wires are made into conductive contact with each other at the connection portions by pressing the covered wires from the outside of the resin chips. Thereafter, the pair of the resin chips are mutually melted at the melting surfaces to seal the connection portions.
Consequently, the connection portions of the two covered wires are sealed by the pair of the resin chips such that they are conductively contacted with each other.
However, such a connection structure has a fear that the covered portions of the wires may be broken by an edge portion of the resin chip at an exit of the covered wire between the resin chips. If the covered portion is broken, there is a fear that water may penetrate through that broken portion.